Guidelines for the Development and Application of Crash Modification Factors

2021 ◽  
Author(s):  
Daniel Carter ◽  
Raghavan Srinivasan ◽  
Frank Gross ◽  
Scott Himes ◽  
Thanh Le ◽  
...  
Keyword(s):  
Crash Modification Factors

Development of Crash Modification Factors for Uncontrolled Pedestrian Crossing Treatments

2017 ◽  
Vol 2636 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Charlie Zegeer ◽  
Craig Lyon ◽  
Raghavan Srinivasan ◽  
Bhagwant Persaud ◽  
Bo Lan ◽  
...  
Keyword(s):  
The United States ◽  
Crash Risk ◽  
Limited Sample ◽  
Cross Sectional ◽  
Empirical Bayesian ◽  
Treatment Type ◽  
Crash Modification Factors ◽  
Pedestrian Crashes ◽  
Pedestrian Crossing ◽  
Crash Types

The objective of this study was to develop crash modification factors for four treatment types: rectangular rapid-flashing beacon (RRFB), pedestrian hybrid beacon (PHB), pedestrian refuge island (RI), and advance yield or stop markings and signs (AS). From 14 cities throughout the United States, 975 treatment and comparison sites were selected. Most of the treatment sites were selected at intersections on urban, multilane streets, because these locations present a high risk for pedestrian crashes and are where countermeasures typically are needed most. For each treatment site, relevant data were collected on the treatment characteristics, traffic, geometric, and roadway variables, and the pedestrian crashes and other crash types that occurred at each site. Cross-sectional regression models and before–after empirical Bayesian analysis techniques were used to determine the crash effects of each treatment type. All four of the treatment types were found to be associated with reductions in pedestrian crash risk, compared with the reductions at untreated sites. PHBs were associated with the greatest reduction of pedestrian crash risk (55% reduction), followed by RRFBs (47% reduction), RIs (32% reduction), and AS (25% reduction). The results for RRFBs had their basis in a limited sample and must be used with caution.

Developing Crash Modification Factors for Horizontal Curves on Rural Two-Lane Undivided Highways Using a Cross-Sectional Study

2017 ◽  
Vol 2636 (1) ◽  
pp. 53-61 ◽  
Author(s):  
Lingtao Wu ◽  
Dominique Lord ◽  
Srinivas Reddy Geedipally
Keyword(s):  
Regression Models ◽  
Cross Sectional Study ◽  
Highway Safety ◽  
Sectional Study ◽  
Cross Sectional ◽  
Highway Safety Manual ◽  
Horizontal Curves ◽  
Before And After ◽  
Crash Modification Factors ◽  
Curve Radius

Horizontal curves have been identified as experiencing more crashes than tangent sections on roadways, especially on rural two-lane highways. The first edition of the Highway Safety Manual provides crash modification functions (CM functions) for curves on rural two-lane highways. The CM functions proposed in the manual may suffer from both outdated data and analysis technique. Before-and-after studies are usually the preferred method for estimating the safety effects of treatments. Unfortunately, this method is not feasible for curves. Previous studies have frequently used regression models for developing CM functions for horizontal curves. As recently documented in the literature, some potential problems exist with using regression models to develop crash modification factors. This research utilized a cross-sectional study to develop curvature CM functions. Curves located on Texas rural two-lane undivided highways were divided into a number of bins based on the curve radius. Safety was predicted with the assumption that these curves had been tangents. The observed number of crashes that occurred on the curves was compared with the dummy tangents and for different bins. The results showed that the horizontal curve radius has a significant role in the risk of a crash. From these results, a new CM function was developed. The prediction performance of the Highway Safety Manual CM function was compared with the new CM function in this study and another function that was recently proposed in the literature. It was found that the new CM function documented in this study outperformed both.

Development of Crash Modification Factors for Uncontrolled Pedestrian Crossing Treatments

2017 ◽  
Author(s):  
Charles Zegeer ◽  
Raghavan Srinivasan ◽  
Bo Lan ◽  
Daniel Carter ◽  
Sarah Smith ◽  
...  
Keyword(s):  
Crash Modification Factors ◽  
Pedestrian Crossing
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